Many folks have trouble digesting fats. I use an enzyme that is especially for fats - it's bile acids by Jarrow. If you are actually killing yeast, you may be experiencing a die-off herx. In other words, when the bugs die, they expel toxins which can get absorbed in the system and cause all kinds of problems. Two thoughts: first, go slow. Start with a very small amount and build up as you feel can. Second, have you cleaned your detox pathways? The body needs to get the toxins out - that requires colon cleansing, liver cleansing, etc.
If I still experience that sick detox reaction, one very effective thing is an enema bag. Here's some other info:
Colon cleansing: http://www.successfulhealing.com/Oxy-powder-article.htm